Field trial removing tiles from NTP if URL is already open - for 1993 clients

chrome/browser/history/most_visited_tiles_experiment.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/history/most_visited_tiles_experiment.h"
+
+#include "base/metrics/field_trial.h"
+#include "base/metrics/histogram.h"
+#include "base/strings/string_util.h"
+
+namespace history {
+
+namespace {
+
+// Constants for the most visited tile placement field trial.
+// ex:
+// "OneEightGroup_Flipped" --> Will cause tile 1 and 8 to be flipped.
+// "OneEightGroup_NoChange" --> Will not flip anything.
+//
+// See field trial config (MostVisitedTilePlacement.json) for details.
+const char kMostVisitedFieldTrialName[] = "MostVisitedTilePlacement";
+const char kOneEightGroupPrefix[] = "OneEight";
+const char kOneFourGroupPrefix[] = "OneFour";
+const char kFlippedSuffix[] = "Flipped";
+const char kDontShowOpenURLsGroupName[] = "DontShowOpenTabs";
+
+// Minimum number of Most Visited suggestions required in order for the Most
+// Visited Field Trial to remove a URL already open in the browser.
+const size_t kMinUrlSuggestions = 8;
+
+}  // namespace
+
+// static
+void MostVisitedTilesExperiment::MaybeShuffle(MostVisitedURLList* data) {
+  const std::string group_name =
+      base::FieldTrialList::FindFullName(kMostVisitedFieldTrialName);
+
+  // Depending on the study group of the client, we might flip the 1st and 4th
+  // tiles, or the 1st and 8th, or do nothing.
+  if (EndsWith(group_name, kFlippedSuffix, true)) {
+    size_t index_to_flip = 0;
+    if (StartsWithASCII(group_name, kOneEightGroupPrefix, true)) {
+      if (data->size() < 8) {
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_TOO_FEW_URLS_TILES_1_8);

[sky, 2013/07/17 21:30:51]

can't you early return here and 50?

[annark1, 2013/07/22 20:35:34]

Done.

+      } else {
+        index_to_flip = 7;
+      }
+    } else if (StartsWithASCII(group_name, kOneFourGroupPrefix, true)) {
+      if (data->size() < 4) {
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_TOO_FEW_URLS_TILES_1_4);
+      } else {
+        index_to_flip = 3;
+      }
+    }
+
+    if (data->empty() || (*data)[index_to_flip].url.is_empty()) {

[sky, 2013/07/17 21:30:51]

Can data ever be empty and can a url ever be empty?

[annark1, 2013/07/22 20:35:34]

Not so far as I can see. I've removed this code now.
On 2013/07/17 21:30:51, sky wrote:

+      LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_NO_URL_TO_FLIP);
+      return;
+    }
+    std::swap((*data)[0], (*data)[index_to_flip]);
+  }
+}
+
+// static
+bool MostVisitedTilesExperiment::DontShowOpenURLsEnabled() {
+  return base::FieldTrialList::FindFullName(kMostVisitedFieldTrialName) ==
+      kDontShowOpenURLsGroupName;
+}
+
+// static
+void MostVisitedTilesExperiment::RemoveItemsMatchingOpenTabs(
+    const std::set<std::string>& open_urls,
+    std::vector<InstantMostVisitedItem>* items) {
+  size_t i = 0;
+  while (i < items->size()) {

[sky, 2013/07/17 21:30:51]

How about a for loop here and below? It need not increment though, but better
matches what's going on, eg:

for (size_t i = 0; i < ...; ) {

[annark1, 2013/07/22 20:35:34]

Done.

+    const std::string& url = (*items)[i].url.spec();
+    if (open_urls.count(url) != 0) {
+      if (items->size() <= kMinUrlSuggestions) {
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_DID_NOT_REMOVE_URL);
+        ++i;
+      } else {
+        items->erase(items->begin() + i);
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_REMOVED_URL);
+      }
+    } else {
+      ++i;
+    }
+  }
+}
+
+// static
+void MostVisitedTilesExperiment::RemovePageValuesMatchingOpenTabs(
+    const std::set<std::string>& open_urls,
+    base::ListValue* pages_value) {
+  size_t i = 0;
+  while (i < pages_value->GetSize()) {
+    base::DictionaryValue* page_value;
+    std::string url;
+    if (pages_value->GetDictionary(i, &page_value) &&
+        page_value->GetString("url", &url) &&
+        open_urls.count(url) != 0) {
+      if (pages_value->GetSize() <= kMinUrlSuggestions) {
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_DID_NOT_REMOVE_URL);
+        ++i;
+      } else {
+        pages_value->Remove(*page_value, &i);
+        LogInHistogram(NTP_TILE_EXPERIMENT_ACTION_REMOVED_URL);
+      }
+    } else {
+      ++i;
+    }
+  }
+}
+
+// static
+void MostVisitedTilesExperiment::LogInHistogram(
+    NtpTileExperimentActions action) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "NewTabPage.MostVisitedTilePlacementExperiment",
+      action,
+      NUM_NTP_TILE_EXPERIMENT_ACTIONS);
+}
+
+}  // namespace history